1. Field of the Invention
The present invention relates to a nitride semiconductor device and a manufacturing method of a nitride semiconductor substrate, and a manufacturing method of a nitride semiconductor device and more particularly, to a nitride semiconductor device and a nitride semiconductor having an electrode disposed thereon and method for manufacturing the same.
2. Discussion of the Related Art
Recently, nitride semiconductor substrates such as a GaN substrate have been manufactured and various methods for disposing an electrode on the nitride semiconductor substrates have been proposed. For example, a method which is characterized by using the active species in a dry-etching for removing a damaged area that occurred by a polishing treatment has been described in Japanese Patent Publication Nos. 2003-347660 and 2004-6718.
However, in a conventional method employing dry-etching, an electrode disposed on a substrate which has been subjected to an etching process can establish ohmic contact only after subjected to a heat treatment, and there have been problems in thermal stability and reliability. Also, in a non-alloy electrode which is not subjected to a heat treatment, it has been difficult to establish a sufficient ohmic contact. If the thermal stability of the substrate-side electrode is poor, the electrode characteristic deteriorates by a heat treatment when mounting the substrate-side of the electrode on a submount such as a heat sink. Therefore, it has been difficult to utilize a device having a counter electrode on the substrate. Also, heat generated during the operation causes deterioration in the ohmic characteristics and a decrease in reliability, and these problems hinder achieving a long life.
Therefore, the object of the present invention is to provide a nitride semiconductor device having a substrate electrode capable of establishing an excellent ohmic contact with a nitride semiconductor substrate. In the present specification, a substrate electrode means an electrode disposed on the substrate.
Another object of the present invention is to provide a highly reliable nitride semiconductor device having a non-alloy electrode which has excellent thermal stability and is capable of establishing an ohmic contact with the nitride semiconductor substrate without being alloyed.